Hello Pragmatist, and welcome to the thread.
First I should explain that I was responding to the assertion that reverse causality
broke the known laws of physics. I responded by arguing that QM implies that reverse causality does indeed occur. You have then argued, based on schroedingers cat, that it
might occur, but it depends on your interpretation of QM.
For my purposes, in the context of this thread, the fact that it might occur is all I need, since I was responding to an assertion that it couldn't occur. Having said that, I believe that other area of QM, experimentally demonstrated, do indeed require reverse causality.
Now to your post :
Pragmatist said:
I've been actively looking into this question of exactly what quantum mechanics "predicts" and how, and I keep coming across what appears to be a fundamental error in logic. I may be wrong of course, but so far I can find no evidence that I am. Which reminds me that I need to follow up on the earlier physics thread.
I also believe that current understanding is based on an error, but I think the error is somewhere else - I believe it is in our initial assumption that reality is observer-independent in the first place. If you ditch that assumption, most of the apparently contradictory implications of QM seem to make more sense - in a very natural sort of way. If Berkeley, or Schopenhauer for that matter, had been presented with QM they would both have just nodded their heads and said "I told you so." But idealism is so much anathema to most modern scientists that they will go to hell and back rather than seriously contemplate that it might be the case. You call yourself a pragmatist, and I am also a pragmatist. In most cases positing idealism isn't very pragmatic, and I don't do it. But in this case, it seems to me that it might be the only sensible thing to do. I too could be completely wrong of course, but I am yet to find a reason why I should think so.
I've been looking into the actual history of the development of QM. I can't find ANY explicit proof that what is often touted as "QM predictions" along the lines of Schrodinger's cat has ever been verified by any means at all. What it all comes down to, it appears, is that Heisenberg offered a philosphical view of a particular problem, and that after much argument (and disagreement) between scientists, it was generally accepted because nobody at the time could think of a better explanation - which of course doesn't mean that THIS one was right.
I'd suggest that although nobody at the time could think of a better one, somebody did think of a better one later, and it was Bohm.
Firstly Schrodinger's cat was a parody of QM that Schrodinger introduced to ridicule what he saw as an absurd assumption by Heisenberg. It is not some fundamental tenet of QM. The whole point of his THOUGHT "experiment" - yes THOUGHT "experiment" - WAS to show that all reason and common sense WOULD be violated if the Copenhagen Interpretation of QM was accepted. And take a look at that latter - "Copenhagen INTEPRETATION". Not, "Copenhagen FACT", but INTERPRETATION. In other words it was ONE POSSIBLE "interpretation" of the apparent results of QM, it was NOT an established observation of undeniable fact.
Which alternative interpretation do you personally favour?
Let's look at what is what in QM. Modern QM is based on the idea that the state of a system can be described by a "wavefunction". The wavefunction which is a purely mathematical construct cannot be solved exactly for most systems and to the extent that it can, it gives an "amplitude" for an event. The problem arises when one considers what an "amplitude" actually MEANS. Nobody knows. So it was decided by concensus that one possible interpretation was that the square of the amplitude represents the PROBABILITY of something happening. This seems to work in practise. So we end up with an equation that predicts the PROBABILITIES of events. A probability is NOT a certainty. Now, the probabilities remain only probabilities UNTIL some CERTAINTY is established. In other words, if I bet on a horse race, there is a high probability that the favorite will win. But it remains ONLY a probability until the actual race is run and ONLY when the race is over does it become a certainty. And despite the probability that the favorite WILL win, it remains a POSSIBILITY that some other horse will win.
So if we have to describe the state of the race before the race is run, we have a nebulous cloud of POSSIBILITIES which are weighted by various PROBABILITIES. But anything is possible until the race is actually run, wherein the "wavefunction", "collapses" and the probabilities become certainties. Therefore in a mathematical sense, in the undetermined state prior to the race, we can say that the favorite horse is both a winner AND a loser at the same time (to various degrees of probability). In REALITY we know that is absurd, and the horse cannot possibly be BOTH the winner AND the loser. Just as Schrodinger's cat cannot possibly be both alive and dead at the same time.
Your analogy is almost valid, but not quite. The process of getting from before the horse race to after the horse race is temporally normal. It goes forwards in time. Before the race there are probabilities, and after the race there is a result. But the situation with the wavefunction collapse is temporally reversed. That is why you have had to say the analogy only work "in a mathematical sense.". In the case of QM, the quantum horse race has to be run backwards, doesn't it? The probabilities still exist at a point in time after the quantum horse race has finished.
QM does NOT say that the cat is BOTH alive and dead at the same time, any more than it says the favorite horse is BOTH a winner and a loser at the same time. ALL it says is that there are certain probabiliites that these things will BECOME so (one way or the other) when the matter is actually resolved.
"will BECOME" and "when the matter is resolved" indicate that the "becoming" and the "resolution"
will occur at some point in the future. But at the point in time at which we are speaking (form the POV of materialist physics with normal linear time), the event we are talking about
has already occured. It seems to me that your analogy doesn't really help, because it doesn't address the real problem here - which is our understanding of time.
These probabilities are based on the PRE-EXISTING known states of the system under analysis. If the system was subject to "reverse causality", then those initial states would be wrong.
And if they are wrong, the wavefunction based on them would be wrong. And if that was the case, the probabilities would change. You would end in a perpetual loop of oscillating conditions. In reality this doesn't happen.
Again, I think you are making too many assumptions about causality. In this case you seem to be seeing causality oscillating about backwards and forwards in time. Can I suggest that instead what is happening is
two different types of causality. In other words that there is normal deterministic forward-pointing causality that we know and love but also a sort of backward causality which is implied by QM and which may form the basis of a future re-assessment of various other questions connected to this one. Because these two forms of causality are not the same, there is no oscillation. Instead, they work together, rather like free will and determinism work together for a compatibilist.
As for Schroedinger - here is something else he wrote :
FOR PHILOSOPHY, the real difficulty lies in the spatial and temporal multiplicity of observing and thinking individuals. If all events took place in one consciousness [italics Schroedingers], the whole situation would be extremely simple. There would be something given, a simple datum, and this, however otherwise consituted, could scarcely present us with difficulty of such magnitude as the one we do, in fact, have on our hands.
The same essay ends with the words :
For eternally and always there is only now, one and the same now; the present is the only thing that has no end.
If you think about it like Schroedinger does, everything just seems to suddenly make sense. I believe that when you change your way of looking at a problem and suddenly everything makes sense it usually indicates that you are heading in the direction of the correct solution to the problem.
